JP2001271108A - Method for producing molten iron using rotary kiln - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a ratio of recovering molten iron, to save an energy and to reduce a producing cost of the molten iron. SOLUTION: In the producing method of the molten iron by using petroleum coke in particular as outer charging coal and a rotary kiln for reducing and melting an iron oxide-containign raw material, the petroleum coke whose grain size of the outer charging coal is used is in the range of 0.5-4 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing molten iron using a rotary kiln.

[0002]

2. Description of the Related Art The prior art of a method for producing molten iron using fine ore, steelmaking dust and the like as raw materials will be described.

First Prior Art A typical technique for the same purpose is a Welz method, and a reduction reaction using a rotary kiln is an SL-RN method or a Krupp-Len method. However, in these first prior arts, before charging the raw material into the furnace, it is necessary to perform a lump-forming process to obtain a lump raw material.

Second Prior Art For the purpose of steelmaking dust treatment and direct reduction ironmaking, an Inmetco process and a Fastmet process using a rotary hearth furnace are known. However, even in the second prior art, the raw material must be made into a lump by performing a lump-making process before charging it into the furnace.

Third Prior Art In Japanese Patent No. 2,789,331 entitled "Method and Apparatus for Recycling Waste Generated from Steelworks and the Apparatus therefor" by the applicant of the present invention, a rotary kiln is used to leave powder or dewatered cake. Raw materials are charged directly, and no pretreatment is required.

[0006]

In the third prior art, the pretreatment of the raw material is not required before charging into the furnace.
It is necessary to further improve the recovery rate of molten iron, reduce the amount of carbon material used as a reducing agent, and further save energy and reduce costs.

It is an object of the present invention to improve the third prior art to improve the recovery rate of molten iron, save energy, and reduce the cost of producing molten iron.

[0008]

An object of the present invention is to provide a method for producing molten iron using a rotary kiln according to the present invention, that is, using petroleum coke as an exterior coal. A method for producing molten iron using a rotary kiln for reducing and melting a treated material, wherein the particle size of petroleum coke as an exterior charcoal is in the range of 0.5 to 4 mm by a method for producing molten iron using a rotary kiln, Achieved.

In a preferred embodiment of the present invention, as described in claim ₂ , a substance containing CaO and SiO ₂ is added to the rotary kiln together with the object to be treated for component adjustment, and the basicity (CaO / SiO ₂₎ is adjusted. ₂ ) 1.5
The range is preferably at least 2.0.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for producing molten iron using a rotary kiln according to an embodiment of the present invention will be described with reference to the accompanying drawings.

Fine iron ore, steelmaking dust, and the like are used as the iron oxide-containing workpiece.

Although a solid reducing agent is also charged into the rotary kiln, usually, carbon materials such as coal, coal coke, and petroleum coke are used.

Before charging into the rotary kiln, the carbon material to be mixed with the iron oxide-containing workpiece in advance is called "interior coal"
On the other hand, what is charged separately from the iron oxide-containing workpiece when charged into the rotary kiln is referred to as “exterior coal”.

As the interior charcoal, the average particle size is about 70 μ100
%, But a relatively large particle size is used as the exterior charcoal.

[0015] This is because fine carbonaceous material is more active in the reduction reaction, and iron oxide (Fe) in a relatively low temperature region.
O, Fe ₂ O ₃ ) and carbon. on the other hand,
In this temperature range, the outer coal having large particles serves as an antioxidant for the generated reduced iron. Also, at the end of the reduction by gas-solid reaction, carburization of the solid reduced iron occurs, and iron saturated with carbon starts to elute. This carburization mainly serves as the exterior coal. Therefore, the particle size of the exterior coal,
The amount and type are important and determine the speed of the carburization reaction.

FIG. 1 is a graph showing the relationship between the reduction rate and the type of carbon material. This is a result of an experiment performed using blast furnace dust as an iron oxide-containing workpiece. It can be seen that reoxidation of coal and coal coke occurs at around 1100 ° C., while reduction of petroleum coke with a small amount of ash progresses in a temperature range up to 1300 ° C. This is Fe
In the presence of O, the ash of coal or coal coke produces a low-melting compound and melts in a temperature range of 1100 ° C or higher,
This is probably because the reduction reaction is inhibited. Fe ₂ O
_It has been found that when blast furnace dust containing a large amount of ₃ or calcium ferrite is used as an iron oxide-containing treatment object, it is effective to use petroleum coke as an exterior coal.

FIG. 2 is a graph showing the relationship between the required external carbon reduction equivalent and the basicity of the material to be treated when the iron recovery rate is fixed at 50%. Petroleum coke is used as exterior charcoal. Basicity (CaO / SiO ₂₎ is from 0.6 to 0.
Group A of No. 8 had blast furnace dust and basicity of 1.3 to 1.5.
Group B is steelmaking dust and has a basicity of 2.0 ~
Groups C and D of 2.5 are the results of experiments on stainless steel dust.

When the basicity is low, as described above, 1100
In the carburizing region at a temperature of not less than ° C., the dust to be treated is liable to be melted and welded, and the molten iron produced by reduction is also entangled in these melts and reoxidized, with the result that the iron recovery rate tends to decrease. Therefore, in order to make the iron recovery rate 50%, an excessive amount of carbon must be introduced as shown in FIG. 2, and reoxidation is prevented by this large amount of carbon.

Therefore, it has been found through experiments that the basicity of the material to be treated needs to be 1.5 or more in order to make the required amount of the exterior coal 2 equivalents or less.

As described above, the armored coal acts as a reducing agent, and when the reduction is completed, functions as a carburizing agent to lower the melting point of reduced iron. If the particle size of the exterior charcoal is too small, it will be consumed by combustion or reduction reaction,
Conversely, if the particle size is too large, the reduction reaction or carburization reaction does not easily proceed because the specific surface area is small.

FIG. 3 is a graph showing the relationship between the iron recovery rate and the particle size of petroleum coke. It is a graph obtained from the experimental results, and it was found that when petroleum coke having a particle size range of 0.5 to 4.0 mm was used as the exterior charcoal, the iron recovery was 50% or more, which was favorable.

The required amount of the interior coal is a chemical equivalent of 1.0.
-1.5, preferably 1.2-1.5. That is, it is a chemical equivalent required to reduce iron oxide in the object to be treated, and is a value indicating how many times the theoretical value.

[0023]

In the method for producing molten iron using a rotary kiln according to the present invention, petroleum coke is used as the outer coal and the particle size is in the range of 0.5 to 4.0 mm. Rate can be improved. As a result, the production capacity of the rotary kiln is substantially improved, and manufacturing costs can be reduced.

Further, in the method for producing molten iron using a rotary kiln of the present invention, petroleum coke is used as an exterior charcoal, the particle size is in the range of 0.5 to 4.0 mm, and the basicity of the material to be treated is 1. Since it is 5 or more, preferably 2.0 or more, the required equivalent of the exterior coal is 2 or less. As a result, the required amount of exterior coal is reduced, and iron production costs can be reduced.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a reduction rate and a type of carbonaceous material.

FIG. 2 is a graph showing a relationship between a necessary external carbon reduction equivalent and a basicity of an object to be treated when an iron recovery rate is fixed at 50%.

FIG. 3 is a graph showing the relationship between the iron recovery rate and the particle size of petroleum coke in the exterior coal.

Claims (2)

[Claims] 1. A method for producing molten iron using a rotary kiln for reducing and melting an iron oxide-containing object to be treated, wherein petroleum coke is used as the exterior coal, wherein the particle size of the petroleum coke is 0. A method for producing molten iron using a rotary kiln, which is in the range of 0.5 to 4 mm. _2. A substance containing CaO and SiO ₂ for component adjustment is charged into a rotary kiln together with the object to be treated, and a basicity (CaO / SiO ₂ ) of 1.5 or more, preferably 2.0 or more. A method for producing molten iron using the rotary kiln according to claim 1.